Closure members associated with office furniture, such as drawer fronts and cabinet doors, are conventionally provided with key-operated rotary lock cylinders which actuate either a linearly or angularly movable dead bolt to permit locking of the closure member. Such lock cylinders are normally rotatably supported within a shell, the latter being fixedly positioned within a bore which extends through either the closure member or an adjacent stationary support. While such locks are notoriously well known and have been utilized with office equipment for many years, nevertheless such locks have been only marginally satisfactory in view of the inability to provide for the desired stroke or displacement of the linearly movable dead bolt, without increasing the overall size of both the shell and cylinder, which is obviously undesirable. Further, in some instances, the inability to provide a proper dead bolt stroke has required utilization of some other type lock, or the adaption of additional linkages or mechanisms. Such alternatives are normally expensive, result in more cumbersome structures, and hence are not of optimum design.
Thus, it is an object of this invention to provide a lock of the aforesaid type, which lock enables the reciprocal travel of the dead bolt to be significantly increased without changing the size or diameter of the rotary cylinder and its supporting shell, and without requiring additional secondary or complex mechanisms or linkages, whereby the improved lock of this invention thus overcomes the disadvantages associated with prior locks of this general type.
In the improved lock of this invention, the key-operated rotary plug or cylinder is supported within a shell which is fixed to either the closure member or the surrounding support frame. The rotary plug, as it is conventional, has an eccentric lug or tenon which projects axially from the inner end thereof, which lug engages within a transverse slot formed in the opposed face of the dead bolt to cause reciprocal slidable displacement thereof in a direction perpendicular to the rotational axis of the lock. This structure, as thus far described, is conventional with locks of this type. The linear displacement (i.e., stroke) of the dead bolt in this conventional lock is equal to the effective plug diameter, which effective diameter is equal to twice the radial distance from the plug rotational axis to the center of the tenon. According to the improvement of this invention, however, the rotary plug has a second eccentric lug or tenon projecting axially from the inner end thereof, which second lug is angularly spaced a substantial distance from the first-mentioned lug. The bolt, in the opposed face thereof, has a second slot which is closely adjacent but spaced from the first-mentioned slot. During rotation of the plug through a selected angle, such as 180.degree., one of the lugs engages one of the slots during only a portion of the selected angle to effect linear displacement of the dead bolt through a portion of its stroke. During this initial portion of the rotation, the other lug is being moved into the other slot such that, during the remainder of the rotation through said selected angle, the other lug engages said other slot and causes continued linear displacement of the dead bolt in the same linear direction. The linear displacement of the dead bolt occurs continuously in response to rotation of the plug, and is of a magnitude which exceeds the conventional effective diameter of the plug and of the lugs associated therewith.
In the improved lock of this invention, the shell and the rotary plug supported therein, which plug is key actuated and has suitable spring-urged lock wafers thereon, is provided with a single substantially cylindrical lug or tenon which is eccentrically positioned relative to the rotational axis of the plug and projects axially from the axially inner end thereof. This tenon has its periphery disposed substantially tangent to the cylindrical exterior surface of the plug. The shell has a pair of internal axially-extending slots which are diametrically opposite one another, and coact with the wafers to lock the plug in either of two positions which are angularly spaced 180.degree. from one another, which positions define the locked and unlocked positions of the lock. A platelike dead bolt is positioned directly adjacent the inner end of the plug and has a transverse slot in the front face thereof which has the tenon slidably engaged therein. This structure, as thus far described, is conventional and well known. According to the improvement of this invention, however, the plug is identical to that just described except that it is provided with a second lug or tenon which projects axially from the inner axial end of the plug, this second tenon being identical to the first-mentioned tenon and being both eccentrically displaced relative to the rotational axis, and positioned so that it is substantially tangent to the cylindrical peripheral surface of the plug. This second tenon is substantially angularly spaced from the first-mentioned tenon by an angle which substantially exceeds 90.degree. but is substantially less than 180.degree.. This second tenon is engageable with a second transverse slot formed in the front face of the bolt, which second slot is parallel to the first, and is positioned closely adjacent same but is spaced therefrom by an intermediate land or island. This land does not extend across the full face of the bolt so that the two slots communicate with one another adjacent one end thereof, whereby the tenons can move transversely back and forth between the two slots responsive to plug rotation. During rotation of the plug through its selected angle, such as 180.degree., the two tenons are sequentially moved into the respective slots to effect sequential engagement with and hence linear displacement of the dead bolt through a stroke which exceeds the conventional effective diameter of the plug.
In a preferred embodiment of the invention, the two tenons are disposed so that their cylindrical peripheries are not only tangent to the cylindrical periphery of the plug, but are also disposed so that their cylindrical peripheries are substantially tangent to a line which extends diametrically of the plug, with the two tenons being disposed on the same side of this diametrical line. This arrangement enables the dead bolt to have a linear stroke which is approximately equal to one and one-half times the conventional effective diameter of the plug, which stroke also approaches the maximum diameter of the circular path traveled by a point substantially tangent to the cylindrical peripheral surface of the plug during rotation of the plug.
The improved lock of the present invention, employing two tenons as explained above, is also desirable in that it enables the tenons to be positioned at more desirable angles relative to the slots in the dead bolt, such that the direction of movement of the tenon at its point of engagement with the respective slot is thus directed more significantly in the linear direction of travel of the dead bolt so as to facilitate the driving of the dead bolt, particularly at start-up when same is being displaced from one of its end positions. This improved lock, and specifically the use of the two tenons, thus enables the lock to avoid the positioning of the tenons at substantially dead-center positions when the dead bolt is at its end positions, such as is conventional with known single-tenon locks of this type, and hence this invention avoids the undesirable mechanical advantage or drive-force relationship which exists at such dead-center positions.
Other objects and purposes of the invention will be apparent to persons familiar with locks of this general type upon reading the following specification and inspecting the accompanying drawings.